Telephone exchange system



June 16, 1931. E. P. G. WRIGHT 1,809,832

TELEPHONE EXCHANGE SYSTEM Filed May 16, 1929 2 Sheets-Sheet 1 lNVENTU/P E. P. 6. WRIGHT A TTURNEY June 16, 1931. p, wRlGHT 1,809,882

TELEPHONE EXCHANGE SYSTEM Filed May 10. 1929 2 Sheets-Sheet 2 55 -|l H 4Q m m III "F lll'.ll II II II m mmm mm mm n n u u m m mm mm nrm'u n m m m m m m m m m m m m m m IIF m gm lll lll-lll m m "rm m m mm m m IIP m m m m m m m m m m m IIF'III m m IIF m m m m m m m m m //VVEN7'0R E E 6i MIGHT i aw. an

ATTORNEY Patented June l l 6, 1 93 UNrrEosTA ESMOND P. WRIGHT, orjALnwYcn, (Lennon, ENGLanDQAssI GivOR tro wns'rnnn r ELECTRIC COMPANY, rnce ronn'rnn', NEW YORK or New Yon gn'. niconronncrron or mutant-ions Excitation SYSTEM,

Application filed May 1'0, 1922 Serial 17 5561912;anathema nrit ia'se tembe 5, 192s.

This invention relates to automatic or semiautomatic telephone systems. The object of; this invention is to provide a trunkingar-:- rangement utilizing a Strowger switch hy' means of which the sizesiofthe groups or" trunks terminating in" the banks of such switch may be varied to any clesiredextent within the totalcapacity of the switch where' by greater economy in the use 033- thecontacts.

of the switclriseiiected and more efiicient grouping oftrunksis realized. w hen two-coordinate switches are em ployed in such systems, particularly when switches are used having contacts arranged in levels so that the brushes of a switch are first moved to select a level and thenatcontact in that level, the arrangement or" lines in groups'becomes very inflexible. For example in the Strowger system groups are practically limited to ten trucks each, although traflicrequirements may only necessitate fewer trunks than ten in one group, and more trunks. than ten'in another group; Arrangements have been devisedby which there maybe twenty trunks in agro'up, by' the use ofm'ore than one setof brushes. In thiscasereithen all groups must consist of twenty'trunks, or

contacts of groups not amounting to twenty be wasted. V I

Arrangements are arrangements are applicable only to selector switches in an end stage in a train ofselectorsp They are, however, 1nap'pl1cable to the ar rangementof trunklines connectingeswitche's in earlier stages of a system bec'ausetne time taken to hunt successively over a. number of contacts; greater than 1611,15 greaterthan the,

time elapsingbetween the dialing: of successive digits.

'lccording to the. present invention a seleca tor switchis provided which is capable of use at any switching stage of a system in "which a group of trunk lines terminates n more than one level, provisionheing madefor simultaneously testing for anidle trunk in two levels. g

In the emhodiment'of the invention chosen for the purpose of illustration a group selecfltor switch of the;- Strowger type. having ten levels of ten contacts each having access to tell level, a set of contacts is left-spare fora purgroups of trunks lie 5 provided: Certain groups,however,:do not occupythe whole of aK pose later to be described but theremaining 1 contacts are utilized as overflow contacts from agroup or groups on another lBVGlr' There needihe norestriction as to the level on which these overflowcontacts appear and, they may be; distributed over more than one level; 'These overflow contacts be either contiguous or non-contiguous to 1 the level I in whichthe 'main group of contacts terminate.

f To a'gro'up 2of such selector switches is multipled a control circuit I hereinafter called a controller containing theirelays for oontrolling 'the motion of the switch. The controller comprises a selector switch iof the same kind 'mechanically'asthat first mentioned, which fcont'roller maybe temporarily associated with an idlejoneof the selector switches upon thecontroller and associated selector switch are-connected also to contacts of the controller If theselector trunk lineand the-controllerswitch which switch is'stepped in a rotary direction to the end {of the particularrban'k level to which it areistepped'verticallyin unison in response to; impulses dialed and are then stepped in rotary hunting movements. The overflow contacts T of'a group appearing in a level of the selector also known inewhi ch a 3 group of linesleading to a private branch ex change may be of any desired SlZ'G,'bt1t these:

is positioned to select a trunk group for whlch there are nooverflow trunks the selector I switch ,alone hunts for a; free 1 seizureof a selector switch. The brushes'of '80 switch on a level corresponding to that of the j was positioned inunison'with the selector 1 is extended thereto and the controller switchu released. If the selected group possesses; overflow contacts both switches are set into" motion to hunt for a. free trunk line,the se-H- Y lectoreswitch in the *inainagroupof trunks and the controller switch in the overflow groupf- I. q a Ifith e' selector switch finds a free outlet the controller switch is immediately released. I If the selector switch fails to find a free outlet and the controller switch finds a 'free outlet the connection is switched through to of this small-switchers then. energized in. a

disclosed in :Fig. 1.,

276,734, filed May .10,'1928. In .the, follow,

the line found over brushes of the controller switch. The next set of impulses dialed may then control the selected switch in the next switching stage, the pulsing circuit extending over the. brushes of the controller switch. The. release magnetof the selector switchisthen energizedto release that switch but the circuit thereof remains connected to the. controller circuit. The controller also includes a small switch often contact sets and. having two banks and brushes. Its contacts are connected to contacts of two extra .levelsofithe cons. tnoller switch, the brushes of-which .are-connectedto ground. The; vertical magnet of the selector switch and: the stepping magnet.

series of steps until the. small switch reaches apoint marked by the vertical position-of the controller switch. The small switch is:. then returned to IlOI'Illfllzfil'ld the rotary magnet. of the selector switch and the magnet of the small switch'are energizedin a series. of steps until the contact corresponding to the level'contact on. which'the controller switch is. resting. is reached. The. connection. is then switched through over brushes, of the: selectorswitch and the controlleris releaseda Referring. to the. drawings in which one embodiment. of the invention has .beendis. closed, Fig. 1 shows a selector switch and Fig. 2 shows a controlling mechanism common: to a group of selector switches such iasuare.

The selectorswitch 100 of Fig.- Land the controller selector 2000f Fig. 2 are of a modi+ fied Strowger type,each adapted to he stepped 1 vertically in a directive movementriand to hunt" in a rotary movement. The auxil-a iary 'or-pilot switch250 ofFig; 2 is a rotary; stepping switch. In general theoperation of. the selector 100 under the controlofthecoms mon controller of. Fig- 2 is in 1 accordance with the method of'operation fully setqforthi, in the application of E. P. G. Wright,-;J. E. Baker, and.A.;H. Cameron, SerialNo.

ing=description which may. bereferred to. for a more complete understanding Offillfl. invention, eachrelay has been designated by a letter or. numeral and each armature. or movable contact .of each. suchrelay by a, suffix; numeral. For. example, in tracinga circuit closed through the. upper middleacon: tacts: of relay Hzrthese relaycontactswill he. referred to as H'4 hack,-if the relay H is at the timedeenergized and,-:H+4- front, if it is: at-the timezenergizedr It: will. be: assumedthat a connectionchasgv been extended by anyuwell known type of." selector, for example such as is shown inthex Patent No.- 1,580,929 issued toRcL. Stokely April 13, 1926, to the selector 100 over the trunk conductors 101, 102 and 103 and that both the selector and the common controller of Fig. 2 are at the time idle as will be indicated by the presence of low resistance battery on the. test conductor 103. A circuit willthereupon be established from ground at the. preceding selector over conductor 103, H2, primary oil-normal springs PON-3 of selector 100, the lower winding of relay K, conductor 104 to battery, through the lower winding of relay 2 and in parallel therewith from conductor 104, over primary oif-normal springs PNC-3 of controller selector 200, oil-normal springs AN-2 of auxiliary switch 250 .to battery throughthe contact-2-2 and the upper non-inductive winding of relay- 2.

. Relays Kand. 2.0perate in this circuit, relay 2 removing its non-inductive windingfrom :.the test circuit to mark the selector 100 and controller as busy to other selectors having access to them.

Acircuit isnow effective for the pulsing of relay 1 extending from battery, contacts 1 normal,;winding of relay 1, contacts P-4 back, conductor 105, contacts K-10, contacts. H5 normal, conductor 101 over the dialing loop, returning'over conductor 102, contacts H6 normal, contacts K-11, conductor 106,.contacts P5 back to ground.

Relay 1 energizes and closes a circuit for slow releasing relay 9 extending. from battery, through the winding of relay 9,.contacts11 .front to groundat contacts P-2.. Relay9 upon energizing closes a holdingrcircnit for relaysy2 and Kirom battery through the lower winding of relay 2, conductor 104, the lower winding of relay K, contact K-3 front,.conductor 107; to groundat contacts 9..3, and connects. ground frompconductor 107,.over' contacts K2, thence as previously traced tothetest conductor 103. 1

Relay 1. responds to impulses transmitted over the dialing loop and completes circuits for the verticalmagnet V1 of selector 100 and for the vertical magnet V2 of. selector 200; The circuit of magnet V1 extends from battery-,through thewinding otthe magnet, contacts K-4, conductor 108, contacts 94 front,.contacts 5-3 toground'at contacts 1-2. The circuit of: magnet. V2.extends from battery-,through the winding of magnet V2, winding-of slow-releasing relay 3, 011'- normal springs PNC- 2, contacts 5-1, contacts .9 1,contacts 11 back, contacts P2 to ground. Relay 3 energizes upon the firstimpulse and being slow to release remains energized Hill .the train of impulses ceases,

and closesan alternate pathfor itself" and inagnet V2, extending over its contact 3-1, the initi al path being opened at the off-nor mal:spmngs PNC2 when'the selector 200 steps one step vertically. Relay 3 at itszcom tact 3-3 frontalso completes an. obvious circuitfor relay 6 which upon energizing locks over its winding andcontacts 6 '.2 front,

conductor 109, contacts K-8,, primary off- "thence through the interrupterjsprings of rotary magnet R1, contacts H- 3,lcontacts K-9, conductor 110, contacts 64- to ground.

Relay 3 also completes a circuit for relay 7 k from battery, through the inding of relay 'r", off-normal springs PNG-4, interrupter springs of rotary magnet R2, contacts 32- front to ground. Relay 7 locksioverthe circuit just traced to ground at its contacts72 independent of relay 3. V

stepped in a rotary direction by the energization of magnet R1 in a circuitextendlng trom 0 3-3 back to ground. As soon as selector100 takes one rotary step the circuit of vrelay 6 contacts K8, off-normal springs PON'-2,

interrupter springs of magnet R1, eleventh R1, extending as previously traced toconground at contacts 3+3 back. Relay 4 maintains itself energized until the'tinterrupter] springs of magnet R1 openoverz-a c1rcu1t which may be traced from battery, through 0 the Winding of relay 4, thence as" previously traced to springs PON2,wthe interrupter springs of magnet Rlfcontacts H- 3, con-j;

tacts K-Q, conductor 110,*to ground atscontacts 42. Relay 4 and magnet R1 thus-op eratesreciprocally until the testf brush 112 encounters an idle trunksterminal. 1 In the meantime 'acircuit is, closed for the rotary magnet R2 of the selector 2001extend- Y ing front battery, through the magnet R2, contacts 71, contacts '32 back; to ground.

The Ienergization of ma'gnet R2 'opensthef stitute a single completettrunk ',group,for example, to the second level, In this jcas'ethe test contactsvof thesecondslevelof'the upper bank of the controller selector200 will be the inding ofrelay 7, off-normal springs 5 PNC-4, interruptersprings of rotary mag battery, Winding of magnet R1, contacts K6, conductor 111, contacts 61, contacts step springs'S1, contacts H4 back, test; brush 112, and the test terminal of the busy trunk to ground. Relay 4 upon energizing again establishes the circuit of rotary magnet duct'or 111, thence rover contacts pto l artificiallybusied by ground connectedthere's to and when the magnet -R2'has frotated the selector shaft one step,.[a circuit for; relay; "Z will be established from battery, through -net R2, rotary eleventh step springs CS-3, contacts O4 back, brush 201 to ground on the strapped bankxterminals with Which brush .201, cooperates, Relay 7 again establishes'ith'e vpreviously traced circuit for magnet 5R2'and thereupon magnet R2 and relay7 interact to rotate the brushes 200 into their eleventh rotary step position where the 1 V circuitof-relay7 is opened at the, springs iCS-fijarld the further" stepping of the selector is'arrestedl I l s v I a The. selector 3100 has, in: the meantime stepped in ahunting movement in search for an idle trunk terminating in its second s bank level. During this stepping a circuit At the end of the train of impulses relay 3 releases and the brushes of selector 100are extends ,from battery, through the Winding of relay4, contacts -2 bacln conductor 109, contacts'IG-Sbtl-normal springs PON2, interrupter springs of magnet R1, springs S-1,:, upper Winding of relay H, springs 5+2, contacts K2 to, ground on conductor .107, Aszlong,however, as ground is encounteredby the test brush 112'testing busy trunks,

is opened. It the first line in the selected level is busy, relay 4 energizesover a circuit extendingfrom battery, throughthei windm'g of relay 4, contacts 62 back,con'ductor 109,

,to energizein series thereW-ith.' At its contacts-'H l5r and,H- 6r relay H connects the trunk; conductors 101 and 1102 through to the brushes'113 and 1140f theiselector 10 0 and opens the previously traced pulsing circuit mum winding of relay 1. "Relayl thereupon,

releasesg'followed byathe release of relay .9.

ing circuit of relays K and When relay 2; de energ1zesa circuit for release magnet lished from battery through the Winding of ,Relay9 upon deenergizing,fopens the hold Z2of theicontroller select0r2200 is estab-Z magnet Z2, ,ofimormal springs PNC 1, to,

ground at contacts 2+1, andthe controller selector is restored 'to normal-and may be taken vfor' usebywanotherselector circuit in thesame manner as previously described. Follow ng therelease of" relay 'K relay H is maintained energized over a circuit extending- 'from battery, through its lower 'W1IiCl111g, "COI1taCtS- Kf9 normal, springs PON -Z, interrupter springs'of magnet R1, sprin s S j1, upper winding of relay H, contacts H-4-front, test brush112 to ground 'at-the succeeding selector.

- Had selector -100hunted to the end'of the bank levelwithout finding 'an idle trunk,

thenfthe eleventh rotary step springs'S would have'operuted, closing a circuit for relay 5 extending from battery, through the WlIltling of relay -5,{-conductor'l15, the eleventh terminal in the second level'ofselector 100,11

, busy 'toneindicatin'g thatjthe call cannot be vtest brush-.112, contacts back, to ground 7' at] springs S+1.' Relay 5 upon operating,

'not be completed' The calling subscriber completed. The-callingsubscriber then hangs: up releasing relay 1 which in turn releases relaysi), 2 and K. Vith relay springs FUN-4, contacts K1 back, con tacts H1 to ground. Upon the deenergization of relay 2, the control selector 200 restores in the manner previously described.

scribed the-selector 100 hunts for an idle trunk terminating in this level. If an idle trunk is found it is seized in the manner previously described. If no idle trunk is found selector 100' rotates its brushes to the blank set of terminals before mentioned whereupon since there is no busy ground on the test terminal, relay H operates and establishes a circuit for relay from battery, winding of relay 5, conductor 115, terminal 116, brush 112, contacts H-l; front, springs S2, contacts K 2, conductor 107, to ground at contacts 9- 3. Relay 5 operates causing the' transmission ofa busy tone to the calling subscriber indicative that the connection canthen restores all operated apparatus in the manner previously described.

In certain cases 1t may be desirable in order to handle heavy tralfie to provide more trunks in a trunk group than can be terminated in a single bank level of'the selector 100. For example, a trunk group terminating in the sixth level of selector 100 may re- 1 quire trunks in addition to the ten which may be terminated in this level and since there are three unused sets of terminals in the ninth level of the selector, a trunk group of thirteen trunks may be obtained by using these three additional'sets ofterminals as an overflow group. To enable this to be accomplished the tip and ring conductors terminating in the eighth, n1nth and tenth sets of terminals in the ninth level of the lower bank of selector 100 are multipled respectively to the first three sets of terminals in the sixth level of V the lower bank of controller selector 200. One'of these trunks 117, 118 has been illustrated as so multipled over conductors 119 and 120. Also thesleeveconductors of these three trunks terminating in the eighth, ninth and tenth terminals of the ninthlevel of the upper bank 01" selector 100 have been shown" as multipled to the first three terminal sets in the sixth level of the upper bank of con- H deenergized a circuit is established for restoring. selec-" tor 100, extending from battery, through the winding of release magnet Z1, off-normal troller selector 200, over conductors 121, 122 and 123.

It will be assumed that a digit is dialed to setboth the selectorlOO and theoontroller seleoton200 opposite their sixth bank levels and that thereafter both selectors start to rotate in their hunting movements in the manner-previously described. The controller selectordoes not, however, rotate automatical- 1y over the entiresixth bank level to its eleventh rotary step position as was the'case when itwasset to its second hank level as previously described but hunts step by step in searclrof an idle trunk of the overflow group terminating in the first three sets of terminals oithis level. If the first trunk in the overflow group is busy, there will be ground potential on conductor 123 connected to the first test terminal of the sixth level of the upper bank of selector 200 and when the test brush 201. makes contact therewith upon the first rotary step of selector 200, the circuit of relay 7 established from battery, through the winding of. relay 7, off-normal springs Filo- 4:, interrupter springs of rotary magnet R2,. springs CS-3, contacts ()4; hack, brush'201' to ground, thereupon again closing the circuit of rotary magnet R21 to advance the selector 200 another step. If the next overflow trunk of the group is also busy, ground potential will be connected overconductor 122 to the next test terminal in the'sixth hank levelof theselcctor 200 and theselector will be caused to advance a further step. As long as busy trunks are encountered, relay 0' cannot'operate as it is shunted. by ground at test brush 2010011- neoted" over a circuit extending through contactsO- i hack, the winding of relay 0, springs CS' 2, contacts 9-6, contacts 6-3 back to ground at contacts 32 back. As soon as'an idle trunk is encountered, however, the shuntvab'out relay 0 is removed at brush 201-,'and relay 0 energizes in a circuit extending from battery, through the winding of relay '7, thence as traced through the windingof relay O to ground at contacts 3-2 back. Relay 7 cannot, however, energize in series w th relay 0. I

In the meantime the selector 100 has been hunting for an idle trunk in the main portion of the trunk group, the trunks of which terminate in the sixth level of thebanks of selectorlOO. If the'selector IOO-has found an idletrunk,relay,1-l operates in the manner previously described thereby releasing the controller selector 200. If, however, the se leetor does not find an idletrunk, it rotates to its eleventh rotary step position, operat-. ing springs S and with relay 0 operated a circuit is established I for relay P' extending from battery, winding of relay P, contacts 0- -1, springs CS1, conductor 124 to ground at springs S 3. Relay P upon energizing opens the circuit of relay 9 but before relay-9 has time to deenergizealcircuitis closed for; releasng selector 100, extending; from battery, through the winding of release,v

: Q IeStlHg the further advance of the selector magnet Z1, ofi-normal springs'BON.e1,con-

tacts K-l. front, conductor. l25,icontacts,

elector 100 have. now been positioned Opposite P6, contacts 2to ground. Theybrushes of selector 100 are thereby restoredto? normal A but the incoming trunk conductors 101,102

I tacts P1, to ground at contacts j2e-3 front j are connected respectively over contacts l-i5 normal, contacts Kl0, conductor1105,

contacts Pet: front to brush 203 and over contacts H-6 normal, contacts 15- 11,, 0011- ductor 106,contacts Pl' 5 front to brush 204 of controller selector 200, thence. to the tip and ring contacts of theaoverflowtrunk which has been seized by the selector 200.

This by-pass connection over'the brushesofl .closes a locking circuit for ltself extending selector 200 enables the. continuation o fedialing to set the succeeding selector without the loss of impulses.

circuit extending through its winding, conand relay O locks in series withthe Winding of relay 7, over its contact 0 4 front, brush 201 to ground at the seized-selector." At contacts O,2 a circuit for holding relays 2 and K operated is closed extending from conductor 107, contacts O 2, conductor 126, i

contacts K 12, contacts H''1 to ground. Circuits-are now establishedtfor repositioning the selector 100 into a position in which i a connectlon maybe made t'o' theitermlnals. I p v I energizes openingthe ClI'CUlt' of'relay 8 which H of the trunk appearing in. the ninth level of its banks which has been seized over mul- 'tiples thereof by the controller selector1 200,

that'is, for stepping the selector 100-to the tenth set of terminals in its ninth bank level; i To accomplish this acircuit is closed from battery, through thewinding of stepping magnet SM of the auxiliary switch 250, contacts ,Y-3 back, contacts 8-2, contacts'9gl j back, conductor l08,"contactsK-4, and. in

parallel therewith to battery "throughi the.

vertical magnet V1 of selector "100, zthence contacts 95, contacts 8-4 backto ground at contacts Y6 back. Each magnet causes its brushes to be advanced a step, the L-magnet 5 V1 opening the stepping circuit at its interrupter springs.- In this manner the selector 7 R1, the circuit of relay 4 is opened at the l interrupter springsof magnetRl and relay 7 l deenergizes','opening the circuits of magnets terminal of its bank which isco'nnected to a terminal of the level to whichtheebrushes of the selector 200-ihave been raised toconnect with the idle'overflow trunkflThis terp p I I I v terminal of selector 200 to which the brushes minal has been; assumed tobe inithe third battery, through the windingof relay 8, contacts Y5 back, brush Si- 1of switch5:250

l and theninth terminal; ofits arc, conductor terminal 206, brush 2'07 to ground. Relay 8 upon energizing opens the previously traced circuits of magnets SM and Vlar- 10,0 and switch 250."The brushes ofsenormal springs AN1 of switch 250 to ground; Relay. Y'HPOD energizing at this vtime operates'only its contacts 2 and thereby relay/Y, contacts Y,1, contacts '81, o-fi' from battery ,t-hroughits two windings, con- V .tacts-Y 2, contacts 23 front to ground. Since relay 8, is still operated, however, the

upperwinding' of rela-y Y is short-cir'cuited and lneifective. A circult 1s now closed for restoring the auxihary. switch 250 which may bet-raced from battery, through the winding" of magnet SM, interrupter springssof mag -net iS M, springs All-3, contacts 8--4;front,

contacts Y '6 back toground'. As-soon as the aux liary sw tch reaches normal thls'stepplng circuit 1s opened at off-normal springs 1Amr']3' "and the short-circuit around the upperwinding of relay'Ynow being opened atol 'f-normalsprings AN1, relay Y fully then releases;

i battery, through the winding of thatrelay, hCOIltHCtS.6 -2 l)t0k, conductor 109, contacts. -K.8, ofi'-normal springs PON2,interrupter springs of magnet R1, contacts Hi-Bf contacts K-S), conductor 110, contacts 8-5 back, contacts Y-dfront to ground. I Relay A energizes closingiat its contacts l'1 a cir- 'c'uitfor magnetRl extending from battery, 1 through the winding of magnetRl, contacts K 6, conductor 111, contacts 4-1., contacts 3; 3,back toground and at its contacts l--.3

closing acircuit forfmagnet SM, extending from battery, through thewinding of magnet, SM,contacts .Y,3 front, contacts 4.3

to ground. Uponxthe first step of selector 100,in response to the. operation of magnet R1 and SM. In this manner relay 4;. and mag nets R11'and'SM reciprocally control each other until the brush S2 of switch 250 is po; 7

sitijoned'upon a terminal connected with a of that selector havebeen rotated to connect set of the sixth level.

'withthe idle overflow-trunk. This terminal has been assumed to be in the third terminal of terminals in its ninth bank level which it will be recalled are multipled to terminals in the sixth level of'the selector 200 upon which brushes of selector 200 are now resting.

With both relays 8 and Y now energized, a circuit is established for relay H of selector 100extending frombattery,through the lower winding of relay H, contacts K7,' conductor 128, contacts 8-5 front, contacts Y6 front to ground. The operation of relay H connects the incoming trunk conductors 101 and 102 through to the tip and ring brushes 113 and 114 of selector 100 in a manner previously described whereupon the dialing circuit over contacts 101 and 102 is extended directlyto the overflow trunk'previously selooted by controller selector 200. Relay H also causes the release-of relays '1 and 2 followed by the release o'frelay9 in the manner previously described. Upon the release of relay Q'the holding circuits of relays P,Y--and 8 are opened and these relays release. The

release of relay 2 also causes therelease'ef selector 200 in the manner described and'the release of switch 250 in a circuit extending from battery, through the winding andinterrupter springs of magnet 'SM, off-normal springs A3 to ground at springs 2+3 back. \Vhen the switch250 reaches normalQthe'circuit of magnet 'SM is opened at offnormal springs AN--3.

The overflow group of trunks need not be confined to a single levelof selector 'but may, as illustrated, comprise-trunks-terminating in terminals of more than one level. For example, in addition to the tr'unkstermina ting in'the ninth level of selector 100 other trunks serving as overflow trunks may also terminate in the eighth, ninth. and tenth terminal sets of the fourth level of selector 100. These trunks are also multiplcd to the fourth, fifth and sixth terminal sets in the "sixth level of the banks of controller selector 200. Thus if the selector 200 in hunting for an idle overflow trunk at the time selector 100 hunts for an idle trunk in the main group, fails to find an idle overflow trunk among the three trunks multipled to the first three termipal sets in its sixth level, it will continue to hunt over succeeding terminals andifit finds an idle trunk, for example-the trunk; multipled to the'fourth terminal set andto the eighth terminal set of the fourthlevel of selecton100,it will seize such'overflow trunk in the manner previously described whereupon the selector 100 is released and is then reset under the control of switch 250 to connect with the multiple of the overflow trunk appearing in the eighth terminal set of its fourth bank level.

If'the overflow trunk multiples do not occupy a full level of the controller selector, the excess terminals are rendered artificially busy by the connection to ground of the test terminals to which the test brush201 has access. Thus if the controller selector hunts over all trunk terminals of an overflow group and fails to find an idle trunk, it steps automatically over the remaining portion of the level until the eleventh step rotary springs CS are operated. If also the selector 100 has found no idle trunk in the main group, the springs S oflsuch selector will also be operated and a circuit will thereupon be established for relay. 5 extending frombat-tery, through the winding of relay 5, springs"CS1, conductor124 to ground at springs S-3. Relay 5 upon energizing causes the transmission of a busy tone to the calling subscribers line in the manner previously described whereupon the subscriber initiates the release of all operated apparatus.

(hat is claimed is:

1. In a telephone system, two switches, each having-operating magnets individual thereto,

connection overv brushes of either of said switches.

2. Ina telephone system, two switches,

means actuated in accordancewith part of thedesigna'tion of a desired'line to cause both switches to hunt simultaneously fora free line within difierent portions of the same group :of lines, means for extending the connection over brushes of either of said switches, means operative if a connection is established over brushes of one of said switches to reset the other of said switches to the line seized by said one switch, and means forthereupon releasirg said one switch.

3. Inatelephone system, a selector switch, 'meansafor actuatingthe switch in one manner :in accordance with part ofthe numerical designation of ardesired line to select a group of trunks,'a second switch, means for actuating the'second switch-in the same manner asand simultaneously with the first switch, and discriminating means actuated in accordance with the size of thegroup selected by the first switch to determine'that either the first switch or 'both'switches shall be actuated in another '4. In a telephone system, a selector switch,

means for actuating the switch in one manner in accordance with part of a numericaldesig, nation ot a desired line to select agroup of trunks, asecond switch adapted upon seizing a tree-trunk to extendthe connection. thereto over its own brushes, means. for completing such connection only after the firstswitch has tested all trunks immediately accessible thereto, means'for actuating the second switch inthe same manner a'sand simultaneously --with the first switch, and discriminating means actuated in accordance with the size of the group selected by the first switch to determine that either the first switch or both hunt fora tree line in a portion of said group of lines, a second switch, means for'moving said second switch simultaneouslywith the first motion of the first switchand thereafter in a hunting movement to hunt for a freeline in another portion otsaid group,and means m'eansfor thereupon releasing the said second switch. A

- -8, In a. telephonesystem, the combination wot a firstswitch,a second switch, a group of lines ofwhichsome are connected to contacts ,of both said switches, means for stepping the fbrushes of these'cond, switch toa particular level and for then rotating said brushesin that level in search for an idle line, a third switch contacts on the said level of the second switch: connected tocontacts of said thirdswitch, means formoving the first switch and thethirdswitch simultaneously, and means torjstopping both'switches when the said third switch reaches l a fcontact connected to a contact of the second switchcorresponding .tothe level in said first switch of the line selected at said second switch. i 9. In a;telephonesystem,,thecombination of a first switch, a second switch, a group of lines of whichsome are connected to contacts not both, said switches, means for stepping the brushes ofthe second switch to a particula-rlevel and for then rotating said brushes'infthatle'velin search for an idle line, a third to'cause turtherselecting motions of the first switch, means for stepping said third switch switch to the line in said other portion of said h group selected by said second switch it all lines in the first portion ofsaid group are '1 found busy, said means comprising means for marking the amount of suchfurthermotion in accordance with the movements of the sec- ;ond switch; c

6. Ina telephone system, a plurality of se- F; lector switches, a control switch common thereto, means for rendering the control switch temporarily individual to one of the selector switches, means for stepping both switches in accordance with impulses rep- I re'sentingpart of the, designation ofa wanted I line, means for thereupon causlngone swltch switch. s

to hunt for a free line within oneportion of a group of lines and for causing the other switch to hunt for a tree line within another A portion of the same group, means responsive to the finding of a tree line by the control switch for positioning the associated selector switch upon contacts of the said line, and means forthereupon releasing the control 7. In a telephone system, in combination, groups of trunks, a plurality of selector switches, a second switch common to-said selector switches, means for actuating the second switch in accordance with part of the designation of a wanted line, means for extends ing a connection over brushes andcontacts z gm with part of theldesignation o a desired line to cause said switch to select a 7 bank level in'which a line group terminates, a second switch operablein unison therewith of the said second switch to an idle trunk in a desired one of said groups of trunks, means l selector switch to the selected trunk, and

for stepping saidfirst'switch vertically in c unison with said third switch to select a levelfthe'rein in .whichsaid idle lineappears, means for then restoring said third switch, means forjresetting saidthird switch to a position ,indic'atedby the contact in the selected level toiwhichsaid second switch'has been stepped,

iandl-mcans for rotatingsaid first switch'in lunison with'said third switchto select'a contact in which said line appears therein.

a plurality of groups oilines terminatingin the'bank levels thereof, means actuated in accordance with part of the designation of a desiredline tocause said switch to select a 110. 111 atelephone system, a switch having I bank level in which a line group terminates,

a second switchoperable'in unisonitherewith.

"to select'a corresponding bank level thereof, means for: causing both of said switches to huntin selected bank levels and-means efiec tive 'if a lineflgroupterminates only in a single bankvlevel of saidfirst switch for cars v ingi thehuntingoperation of said first switch to'seize an idle line and for rendering the "hunting operationlof saidsecond switch-"hr efiectivei e I 11. .1113 telephone system, a switchhaving a plurality'of groups of lines terminating in "the bank levels: thereof,- meansactuated in to @selecta corresponding bank level thereof,

means-for causing/both of said switches to hunt in selected bank'levels,and means efieconly of a single bank level of'said first switch for causing the hunting operation of said I first switch to seize an idle line and for rendering the hunting operation of said second switch ineffective.

12. In a telephone -system, a switch, a group of lines divided into a main subgroup and an overflow subgroup, said main subgroup of lines terminating in a single bank level of said switch andithe lines of said overflow subgroup being dispersed into a plurality of other bank levels of said switch, a second switch in which the lines of said overflow'subgroup are multipled to bank contacts of a level corresponding to the level of said first switch in which the main subgroup of lines terminates, and means actuated in accordance with part of the designation of a desired line to cause said switches to step in unison to select levels in which said lines terminate and to hunt for an idle line.

13. In a telephone system, a switch, a group of lines divided into a main subgroup and an overflow subgroup, said main subgroup of lines terminating'ina single bank level of said switch and the lines of said overflow subgroup being dispersed into a plurality of other bank levels of said switch, a second switch in whichthe lines of said overflow sub- 1 group. are multipled to bank contacts of a level corresponding to the level of said first switch in which'the main subgroup of lines terminates, means actuated in accordance with part of the designation of a desired line to cause said switches to step in unison to select levels in which said lines terminate and to hunt for an idle line, and means for rendering the operation of said second switch inefiective if said first switch finds an idle line in the main subgroup.

14. In a telephone system, a switch, a group of lines divided into amain subgroup and an overflow subgroup, said main subgroup of lines terminating in a single bank level of said switch and .the dines of said overflow of lines divided into a main subgroup and an overflow subgroup, said main subgroup subgroupare-multipled to bank contacts of a level corresponding to the level of said first switch'in which'the main subgroup of lines terrninates,means actuated in accordance with part of the designation of a desired lineto cause said switches to step in unison to select levels in which said lines terminate and to hunt for an idle line, means for rendering the operation of said second switch inefiective if said first switch finds an idle line in the main subgroup, means for restoring and resetting said first switch to the level in which an idle overflow line terminates ifin-hunting itfinds no idle line in said main subgroup and said second switch finds anidleline in said overflow subgroup, and -means for thereafter restoring said second switch.

In "witness whereof, I hereunto subscribe my name this 8th day of April, 1929.

ESMOND P. G. WRIGHT.

subgroup being dispersed intoa plurality of other bank levels of said switch, a second switch in whichthe lines of said overflow subgroup are multipled to bank contacts of a level corresponding to the level of said first switch in which the main subgroup of lines terminates, means actuated in accordance with part of the designation of a desired line to cause said switches to step in unisonto select'levels in which said lines terminate and to hunt for an idle line, means for rendering the operation of said second switch inefl'ective if saidfirst switch finds an idle line in the main subgroup, and means forrestoring and resetting said first switch to the level in which an'idle overflow line terminates if in hunting it finds no idle line in said main subgroup andsaid second switch finds an idle line in an overflow subgroup.

.15. In a telephone system, a switch, a group 

